Color pure cathode ray tube display mechanism



S. L. REICHES June 7, 1960 COLOR PURE CATHODE RAY TUBE DISPLAY MECHANISM 3 Sheets-Sheet 1 Filed April 26, 1957 0L L. RE/Cf/ES 0 ATTORNEYS S. L. REICHES June 7, 1960 COLOR PURE CATHODE RAY TUBE DISPLAY MECHANISM 3 Sheets-Sheet 2 Filed April 26, 1957 COLOR PURE CATHODE RAY TUBE DISPLAY MECHANISM Filed April 26, 1957 5 Sheets-Sheet 3 50L L Rf/CHEJ mrvz/vrma A rr omvt r:

COLOR PURE CATHODE RAY TUBE DISPLAY MECHANISM Sol L. Reiches, Shaker Heights, Ohi (6900 Wade Park Ave., Cleveland 3, Ohio) Filed Apr. 26, 1957, Ser. No. 655,272

1 Claim. (CL313-77} The present invention relates to an improved cathode ray tube display mechanism capable of reproducing color television images in full and pure color. It is a continuation in part of my copending patent applications S.N. 600,314, filed July 26, 1956, entitled Post Deflection Color Purity Correcting Device for a Color TV Cathode Ray Tube and System Using the Same, and SN. 648,471, filed March 22, 1957, entitled Post Defiection Color Purity Correcting Device for a Color TV Cathode Ray Tube and System Using the Same, both assigned to the same assignee as the present invention. Application S.N. 600,314 is a continuation in part of ap plication S.N. 564,197, filed February 8, 1956, hearing the same title, assigned to the same assignee now abandoned.

in one method of producing a cathode ray image in full color, the phosphor screen has small spaced deposits of phosphors divided into color groups, usually groups of three called triads. The individual phosphor deposits making up each group produce one primary color when energized, so that when all are activated the illusion of a full color reproduction is created. A cathode ray gun is provided for each group of-phosphor deposits and is energized in accord with the time variations of the intensity of that color to be reproduced during scanning movement of the ray beam. The ray beams are swept in unison. to reproduce the respective color images simultaneously for blending in the eye of the observer to achieve the desired effect.

Faithful color reproduction bythe above method. demands that at all times the respective ray beams actuate only the corresponding phosphor deposits. Thus, for ex.- ample, one beam should. only energize. the red light. producing phosphor deposits, another only the green, and the third. only the blue. In the shadow mask type tube, this is accomplished by the use of an. apertured plate positioned to permit electrons to reach: the phosphor screen only through the apertures. Since the ray beams are initially spaced, this makes it possible to position a triad or group of. phosphor deposits behind the shadow mask in such position that each deposit. is in the zone of action ofv only the correspondingcathode ray beam.

In actual. cathode ray tube construction, a. number of tolerance factors preclude the faithful reproduction of the respective colors. These tolerance factors include errors in the positioning, and orientation of the respective cathode ray beams; deviations of deflection. yoke action from the theoretically perfect deflection; errors in the positions of the respective phosphor deposits; variations in the distance between the shadow mask. and phosphor screen; and the efiects of stray and the earths magnetic field. In order to overcome these deviations from the theoretical ideal, it has heretofore been the practice to provide various forms of color purity devices efiective to reorient the respective cathode ray beamsprior to sweep and thereby provide some measure of restoration of the color purity.

Heretofore it has been considered essential to direct he cathode ray beams through the so-called color cannited States Patent 0 2,939,979 Patented June 7, 1960 ice ters of the tube-that is the points from which the respective ray beams are assumed to come when the phosphor deposits are made. In consequence, the eflort's to correct for the various deviations from ideal tube per formance have been confined to reorienting and shifting the cathode ray beams prior to sweep. For this reason a variety of convergence or color purity magnet devices have been used; windings have been provided to vary the effect of these devices in unison withthe sweep action to achieve dynamic correction, and a wide variety of adjustments have been provided in an short to achieve some acceptable measure of color purity by aprocess of rcpeated adjustment.

Contrary to the conception heretofore applied, the present applicant has found that it' ispossible to correct for deviations from ideal performance by the use ofmagnets efiective on the ray beams after they are swept. Applicant accepts the fact that in many tubes the respective cathode ray beams do not travel through the color centers of the tube. Instead of attempting to make the ray beams pass through the color centers applicant, in accordance with the present invention, reorients' the electron beams by the use of magnetic fields located between the deflection yoke and the phosphor screen. These fields are conveniently created by the use of a plurality of universally rotatable permanent magnets disposed in a ring encircling the bell of the tube. In the use of' a color purity mechanism of this kind, the beams are initially converged on the center of the viewing screen by suitable convergence magnets efiective on the ray beams before they reach the deflection yoke. The red, green, and blue fields are thenseparately energized and the magnets adjusted to provide maximum color purity witlr'each; While theory would not indicate that this relatively simple and straight-forward technique would lead to adequate color purity, experience has shown that it provides color purity tar superior to that heretofore achieved;- it makes possible the use of cathode ray tubes with deviations from design standards greater than heretofore permitted; itmakes possible larger openings in the shadow mask (especially with a coplanar electron gun type tube) and the incident increased efliciency; and it makes the coplanar gun type shadow mask tube especially effective; Moreover, since the apparatus of the present invention permits use of the central (and most readily controlled) part of the yokes field, the yoke design is not as critical as is otherwise required andin' addition-the position of the yoke along: the neck of the tube is not as: critical as with other arrangements.

It is therefore a general object of the present invention to provide an improved color pure cathode ray tube display mechanism that does not require the ray beams to pass through the respective color centers. A further object of the present invention is to provide a color pure cathode ray tube display mechanism in which the cathode ray beams are reoriented by magnetic means efiective after sweep action;

Another object of the present invention is to provide an improved color pure cathode ray tube display mech anism which utilizes a time constant magnetic field of space-varying orientation and intensity to selectively redirect the respcctive cathode ray beams. Whichthereby provide a high degree of color purity despite imperfections in the tube, the deflection yoke, and otherwise.

Still another object of the present invention is to provide an improved color pure cathode ray tube display mechanism that requires only a. few adjustments and permits a relatively unskilled operator to adjust a color tel'e vision receiver for color pure full color operation.

It is yet another object of the present invention to provide an improved color pure cathode ray tube display mechanism. that, is especially applicable to cathode ray sizewith' the incident improvement in efiiciency, acts on the ray beams uniformly to some extent'and differentially to sorne extent and can be designed to fix these respectiveextents at desired values, and is otherwise a highly effective, practical, construction. a

- The novelfeatures which I believe to be characteristic oftmy invention are set forthwith particularityinrthe appended claims. My invention itself, however, together with further objects and advantages thereof, will best Toe understood by referenceto the following description taken in connection with the accompanying drawing in' which: H a p Figure 1 is a top-plan view of a multi-ray beam cathode ray tube of the shadow mask type with the deflection yokein place and one form of color purity correction mechanism constructed in accordance with the present invention; a

Figure 2 is a view through axis 2-2, Figure 1;

Figure 3 is a fragmentary viewin perspective showing one of the color purity magnets of the mechanismof Figures 1 and 2; 1

Figure 4 is'a fragmentary top-plan view of aportion of the structure shown in Figure 3 and showing an alternative magnet position by dashed lines;

Figure 5 is a cross-sectional view through axis 5-5, Figure ,4 showingvstill another position of adjustment of the magnet of Figures 3 and 4.

. Figure 6 is an enlarged cross-sectional view through i axis 6-6, Figure 1, showing the positions of the electron guns of the tube of Figure 1; V I Figure 7 is a somewhat diagrammatic view through axis 77, Figure 1, showing the magnetic radial ray beam convergence adjusting mechanisms of the apparatus of-Fi'gure 1;' a Y Figure '8 is a somewhat schematic drawing showing I in the structure of Figure 1; 7

- Figure 10 is a view like Figure 2 to a different scale and 7 showing an alternative form of the color purity magnet devicewhich may be used in the apparatus of Figure 1; Figure 1%1 is a view likeFigure 1 but showing a fragmentary portion of a planar gun type shadow mask type cathode ray tube; g

-Figure l2-is a greatly enlarged cross-sectional view through axis 12-12, Figure 11 and showing the location of the electron guns in the apparatus of Figure 11;

Figure 13 is an enlarged cross-sectional view through axis 13 -13, Figure 11, and showing the horizontal static ray'beam'f convergence adjusting mechanism of the apparatus of Figure 11;.

Figure 14 is an enlarged cross-sectional view through axis 14.14, Figure 11, and showing the static vertical cathode ray beam convergence adjusting mechanism of the apparatus of Figure 11; and 'Figure '15 is a horizontal cross-sectional view in somewhat diagrammatic form showing how the outer two ray beams of the apparatus of Figures 11-14 are directed.

The apparatus shown in Figures 1-9 is theform of the present invention which is specifically described and claimedin my ce-pending application, Serial Number 600,314 entitled"Post Deflection Color Purity Correcting Device for a Color TV Cathode Ray Tube and System Usingthe Same, filed July 26,1956, and assigned to the same assignee 'as the present invention. In this apparatus the cathode ray tube indicated generally at 10 has a'neck portion 1015a bell portionlt b, and a, face portion Figure 1, at the shadow mask 20.

100. These define a closed evacuated space and have a common axisA-A. A group of three electron guns 14b, 14:- and 14g are positioned in the neck 10a in a delta or equilateral triangular configuration as shown in Figure 6. These electron guns are electrically connected to the base 12 to receivethetheater current to warm the cathodes to electron emitting temperatures and the voltages required for th'e' various "accelerating and'focusing electrodes and the control electrodes. The guns have a slight inward tiltas shownin Figure 6.to.cause the ray beams to converge approximatelyson the axis AA,

The neck 10a receives theiradial. static convergence mechanism 11 described in detail hereafter and the deflection yoke :16, alsode'scribed hereafter. To the right of the deflection yoke 16 the bell 19b of the tube flares in conical conformation to the sleeve 10d which defines the tube portion of maximum diameter. Toward the front of the sleeve portion 10d and internally of the tube a flat phosphor screen 18 is located. Immediately'in front of this" phosphor screen and in the path o t electrons from the, respective guns 14b, 1 4 r, and,14g, the shadow mask 29 'is located to provide the action hereinafter-described in detail. Thebell portion 10b of thetube receives the color purity magnet assembly indicatedgenerally at 21 which is described in further detail hereafter.

I The radial ray beam static convergence mechanism 11 is shown in detail in Figure 7. As shown, the ray beams 15b, 15g, and 15r travel from the respective'guns toward the face of the tube and at the time theyreach the unit 11 these ray beams have slightly converged towards the axis of the tube. The neck 10a of the tube has three sets of internal magnetic plates 34b, 34g and Mr which, as shown in Figure 7, straddle the respective cathode ray beams. As shown, each of these plates has an arcuate portion which seats against the inner face of the neck 10a. Three convergence magnet units 36b, 36g, and 36r define pole faces in juxtaposition with the respective arcuate portions of the magnetic plates 34b, 34g, and 341', respectively. Each unit 36b, 36g, and -36r-has a cylindrical opening in which is rotatably disposed a permanent magnet, 38b, 38g, and 38r, respectively. Each such magnet is magnetized to define diametrically opposed poles, so that: by rotating the magnets about their respective axes the intensity and direction of the poles defined by units 36b, 36g, and 36r can be adjusted. This effects a corresponding field betweenthe plates of the respective pairs 34b, 34g, and'34r which fields encompass the respective ray beams 15b, 15g, and 15r.= It will be noted that the fields between the pairs of plates 34b, 34g, and 341' are tangential in relation to the axis of the neck 10a. Since the ray beams are deflected in directions transverse to both the direction of ray beam travel and the direction of the magnetic field in each instance, the adjustment of'the magnets 38b, 38g, and 38r serves to converge the ray beams 15b, 15g, and 15r as desired, and to overcome any lack ,of convergence resulting from deviation of the physical orientations of the electron guns from that providingthe desired convergence. As is described in further detail hereafter, the magnets are initially adjusted to converge the ray beams on the axis A- -A Figure 1, and on the shadow mask 20. This convergence is also shown in Figure 9.

The deflection yoke 16 includes vertical and horizontal pairs of coils straddling the neck 10a to produce vertical and horizontal fields in neck 10a and the most narrow portion of the bell 10b. A horizontal coil is indicated diagrammatically at 16a, Figure 1.. It (and its mate, not shown) receives the 60 cycle saw-tooth current ,flow required to generatea horizontal magnetic field of. sufficient intensity to sweep the raybeams in unison in the vertical direction 'over' the'shadow mask 20, and the phosphor screenv 18. A pair of'vertical coils 16b is shown in diagrammatic viewdin'rFig'urel. 'These are'energized with the ,6ki ocye1e'saw-tocth sweep current required ssume to sweep the ray beams in unison cross-wise of the shadow mask 20 and viewing screen 18 to provide the necessary horizontal sweep for reproducing the image. It will be noted that the horizontal coils 16a and the vertical coils 16b are centered upon the plane B--B which, as is described hereafter, is approximately the plane at which the ray beams may be considered to bend sharply during sweep action.

The action of the deflection yoke 16 is approximately to rotate the ray beams about centers defined by the intersections of the plane BB with the respective ray beams. However, in actual practice the yoke deviates from this ideal and tends to introduce color impurities into the system.

The phosphor screen 18 has three sets of phosphor deposits 19. One such set is indicated at 19g, Figure 8, one at 19r, Figure 8, and the third at 1%, Figure 8. These sets of phosphor deposits are in the form of triads or groups of three, one group corresponding to each opening 29a in the shadow mask 26. It will be noted in Figure 8 that when the respective ray beams b, 15g, and 151- converge and pass through the shadow mask opening 26a they diverge in the region between the shadow mask and the phosphor screen 18 so that each strikes a different phosphor deposit, the ray beam 15r striking the deposit fig and the ray beam 151) striking the deposit 19b. The phosphor deposits 19r produce red light when struck by the electrons, the phosphor. deposits 1% produce blue light, and the phosphor dots 19g produce a green light when struck by these electrons. It will be observed, therefore, that the electron streams 15b, 15r, and 15g produce points of red, blue, and green light, respectively, when they converge upon the shadow mask 20 and travel in the correct diverging directions therefrom to strike the intended phosphor deposits.

The respective phosphor deposits on the phosphor screen 18 are positioned in a manner calculated to produce the above action during the entire sweep action of the ray beams. In one method of so positioning the phosphor deposits, a light source is located on the plane BB, Figure l, at the points where the respective light beams 15b, 15g, and 151' should intercept that plane. When the electron guns are thereafter affixed to the complete tube and are located at their intended positions, the tube should, in theory, produce the desired efiect, namely the ray beam 1512 should create blue light only, the ray beam 151 should create red light only and the ray beam 15g should create green light only. In actual practice this ideal condition is not achieved because, in actual tube manufacture, there are always deviations from the ideal conditions and, as well as deviations in the deflection yoke action from the ideal. The result is that the image produced is not pure in color but rather is deficient in its color content and is otherwise unsatisfactory.

In the structure of Figures 1-7, a conical strap 22, Figures 1-5, is received over the bell 10b of the tube 19 and is held thereon by the bolt 24 and the nut 24a which clamp the two outwardly extending ears 22a together as is shown in Figures 1 and 2 to grip the tube. This strap is of a non-magnetic material, such as aluminum. About its periphery a series of adjustable permanent magnet units 25' are mounted. In the particular form shown, a total of eight such units are shown and are located at equally spaced distances about the periphery of the strap 22. The structure of each of these units is best seen in Figures 3, 4, and 5. Each consists of an angle bracket 26 formed of non-magnetic material, such as aluminum. Each such bracket has a foot portion 26:: which seats against the base of the strap 22 and is riveted thereto by a rivet 23, Figures 3 and 4. The rivets secure the portions 26a to the strap 22 while permitting the brackets to rotate about the axes defined by the respective rivets. Each angle bracket 26 has an upstanding F9 1;! 2 which s at right angles to the base 26a and Each of the magnets 32 is magnetized to form (ii-- ametrically opposed poles with respect to the support pins 30. That is, in the structure shown in Figure 3 the end 32a of the magnet is a north pole and the end 32b is a south pole.

It will be observed that each of the magnets 32 may be rotated about the axis of the pin 28 supporting the corresponding bracket, and may be rotated about the axis of the pin 30 which serves to support the magnet itself. The former axis is generally normal to the outside face of the bell part 19b of the tube, and the latter axis is generally transverse to the former. It will be further noted that rotation of the magnets about the rivet or pins 28 brings the magnetic field into more or less alignment with the electron streams, whereas rotation of the magnets 32 about the pins 30 tends to orient the tilt of the magnetic field as it is traversed by the electron streams. The former rotation primarily varies the degree of coincidence of the magnetic field with the direction of ray beam travel and hence the extent the ray beam is deflected. The latter rotation primarily varies the direction of ray beam deflection.

In the use of the apparatus shown in Figures 1 to 7, inclusive, the magnets 32 are first rotated to generally parallel relationship with the axis of the tube by rotating the same about the rivet 28. The receiver is then energized without any sweep current flow (or with a signal providing a cross hatch pattern) and the respective ray beams converged on the shadow mask 20 at the axis AA. This is accomplished by rotating the magnets 38b, 38g, and 38r, Figure 7, until the beams are thus positioned. The blue and green electron guns 14b and 14g are then deenergized and the beam 14r energized. With the sweep system operating (yoke 16 energized with vertical and horizontal sweep currents) the respective magnets 32 are thereupon rotated about their axes 28 and about their axes 30 as is necessary to provide a raster of rectangular shape and uniform red color. It will be noted that to the extent that the sweep system-acting in conjunction with errors in the tube construciton-.-tends to cause the red beam to deviate from its intended function, this will show up at this time in the form of other than red color on the viewing screen. When the magnets 32 have been adjusted as is necessary to give .the

required red'color over the entire viewing screen, the

red electron gun Mr is then suppressed and the blue electron gun 14b energized. The process is then repeated as is necessary to produce a color pure blue raster by the action of the blue gun 14b. Guns 14b and Mr are thereupon suppressed and the gun 14g energized and the process repeated to obtain the maximum color purity with the green color only. 7

In the abQve process a degree of dependence exists between the corrections for the red, blue, and green electron beams. Indeed, it would theoretically seem that the magnet units 32 would be incapable of providing adequate color purity correction inasmuch as when any magnet is adjusted to correct impurities with respect .to one color -it also would seem to afiect adversely the color purity with respect to the other colors. Nothwithstanding this seeming dependence of each color on the other, it has been found that the apparatus shown in Figures 1 to 7 is capable in practical cases of providing selectivity as between the respective electron streams, a high degree of color purity, and a much more satisfactory :operatibri'ithan"can-[be achieved with the previous'neck color'purity'correction devices. This action is believed to' be due, 'inpart at least, to the fact that the electron 1 are spaced from each other and to the fact that the magnetic fields created by the respective magnets 32c);-

-tend within the bell 19b of the tube lllonly to limited extents. i when the ray beams are swept in'unison by the action ofthe deflection yoke 16, they accordingly enter into the fields of the'respectiv'e magnets to varying degrees and because of this variation the ray beam shift associated'with the action of the respective magets is difie'rent for each of the guns. This action isshown in Figure 9" which is a somewhat diagrammatic view showing how'the magnets 32 tend to act upon the ray beams difierentially insofar as the'top edge of the image is con- 7 cerned; As is shown, the ray beams in the absence of V sweep} converge on the shadow mask 20 and pass through 'the axial or central opening therein to spread thereafter and form the center triad of illuminated dots on the view- 1 ing' screen 18. These undefiected ray beams are shown at I4b and-14r' respectively, in Fig'ure9. Neither ray ,beam is at this time affected by the action of the magnets 32, inasmuch as in the'undeflected condition the ray beamsremain outside of the zone of influenceof the 'magnets.- 7 7 The paths 'of the ray beams at'maximum upward ver- 'tical sweep are shown at 14b" and 14r respectively. In' this condition, the ray beams are nowdeflected close in its travel to a greater degree than theray beam 14r,

it follows that the magnets 32-tend to influence the ray beam travel to difiering extents and,- accordingly, they make it possible by repetitive adjustment of the'magnets with the various ray beams energized to achieve by a process of the successive compromises a color image having a high degree of color purity.

. .The extent the magnetic fields act difierentially on the,

raybeams is determined by the physical separation of .the'ray beams where they pass through the zones of influence of the magnets. By moving the magnets closer to the neck of thetube the eflect of the fields on the ray beams is made less uniform-if the magnets are located nearer the shadow mask (wherethe ray beams converge) the efiect on the respective beams is made more uniform. i a

' Figures 11 to 15, inclusive, show an alternative form of the present invention in which the electron guns are in spaced positions on a single plane. As shown in Figure 11, the cathode ray tube 110 is like the tube 10, Figure 1,

in that it has a neck portion 119a, a bell portion 110b, a shadow mask (120, Figure 15, not shown in Figure 11'), a face plate 110:: (shown in Figure 15 but not shown in Figure 1-1). 'The neck 110a'of tube 110 has a horizontal ray beam convergence unit 109 and a vertical ray beamconvergence unit 111 as are described in further detail hereafter. .The front portion of the neck 110a and the rear portion of the bell'110b receive the deflection yoke 116 which has horizontal and vertically oriented windings toreceive the sweep current flow to deflect the ray beams in unison as is above described in connection with yoke 16, Figure '1.

'Figure 12, shows electron guns of the unit of Fig- *on a common horizontal plane BB, extending through the neck of the tube. The gun 114r is additionally located of any magnetic or other ray beam deflection devices,

these beams will tend to converge at the point on the shadow mask 120, Figure 15, where the axisC-C crosses the shadow mask; V

Figure'13 is a cross-sectional view showing the positioning and operation of the horizontal ray beam convergence devices of the apparatus of Figure 11. As is shown, the pair of plates 1341: straddle the ray beam 11% 'in the same general fashion as do plates 34b, Figure 7.

'These plates eachhave arcuate surfaces seated against the interior of the neck 110a which mate with the poles of the magnet core 136b to be energized thereby; A diametrically magnetizedpermanent magnet 138b is rotatably disposed in the core'136b as is shown in Figure .13,

.thereby permitting adjustment of the polarity and intensity of the magnetic field between the plates 1341). Since this is a vertical magnetic field it the ray beam 115b inthe horizontal direction and thus provides an adjustment by which the ray beam 115b may be adjusted to converge with the ray beam 115r on the point the shadow mask 120 crosses the axis C-C. The internal pole'pieces 134g straddle the ray beam 115g just as the pole pieces 134b straddle beam 1151:. These pole pieces are energized from the diametrically magnetized rotatable magnet 138g through the core 136g to vary the intensity and polarity of the vertical field through which the ray beam 115g travels. This provides adjustment of the horizontal position of the ray beam 115g to cause the same to converge on the shadow mask 120 with the ray beam 115r and the ray beam 115b. j V

Figure 14 is a cross-sectional view through axis 14-14, Figure 11, showing the mechanism lilby which the blue ray bearn 1151) and the green cathode ray beam 115g are aligned and converged with the red ray beam 115r. Itwill be observed that the internal pole pieces-133b, when magnetizedbythe diametrically magnetized rotatable permanent magnet 1317b acting through the core are oriented, with aslight inward tiltso that in theabsence 13512, serve to produce a horizontal magnetic field in the region traversed by the ray beam 115b. This field is of adjustable intensity and polarity and'-since it is horizontalit shifts the ray beam 115 in the vertical direction. By appropriately adjusting the magnet 13% it 1s. accordingly possible to orient the ray beam 115b to converge on the shadow mask-1'20 with the central ray beam 1:15r.

, The internal pole pieces 113g coact with the core 135g and the rotatable diametrically magnetized permanent .magnet 137g to produce a horizontal magnetic field of adjustable intensity and direction through whichthe ray beam 115g-travels. 'By rotating the magnet 137g the vertical position of the ray beam 115g may be accordingly adjusted and that beam converged on the shadow mask 120 with the ray beams 115r and 1 15b- Thus, by adjustment of the magnets 138b, 138g, 1371), and; 137g, the three ray beams emanating from the electron guns 114b, 114r, and 114g, may be brought to coiincidence or convergence on the shadow mask :1-20 in the absence of sweep current flow in the deflection coil 116.

In the apparatus of Figures'll-IS 'a post deflection color purifier indicated generally at 121 is provided. This purifier is of construction similar to the post deflection color purifier of Figures 1 to 5. In brief, it includes a non-magnetic strap 122 which is secured about the bell portion 11Gb of tube and carries a plurality of spaced magnets 132, each of which is rotatable about the axis of the bracket support pin 128 and-about an axis transverse theretodefined by its cwn'support pin 130.

In use, the apparatus of Figures 11 to .15 is first energizedwithout'applying sweep, current flow to the deflection windings 116. Preferably, either the blue beam b or the green beam 11517 is deenergized and'the-other brought to convergence on the shadow mask'120 with the red'beam 115r which, in the form of the structure shown, is not subjectto adjustment. Then, the third beam .is adjusted to convergence at the center of shadow 9 m s 12 hhe eth r t a be ms o p e a iad of red, blue, and green colored dots at the center portion of the viewing screen 118. The color purity adjustments are then performed in the same general fashion as with the apparatus of Figures 1 to 5 until the color pure red, green and blue rasters are provided. It will be noted that with the structure of Figures 11-15, the ray beams are on a common horizontal plane. Such deviations as occur from this horizontal plane are very minor once the horizontal adjustment is achieved by adjusting magnets 137b and 137g. Consequently, there is little tendency for the ray beams to lose convergence as they are swept in the vertical direction and there is a corresponding small need for adjustment of the color purity magnet 132 with respect to the vertical sweep. However, the ray beams 11517 and 115g are relatively distant from each other in the neck of the tube and these beams accordingly tend to depart from theoretical perfect performance when swept horizontally of the tube. This is shown in the view of Figure 15 where the ideal path of the beam 115g as deflected is shown at 115g" and the actual path at 115g". Proper adjustment ofthe color purity device 121 sewes to bring the ray beam 115g" into the intended path of travel shown by lines 115g, Figure 15. Thus the eifect is to overcome the deviation from the desired path of travel that would otherwise tend to cause loss of color purity. It might be added that since, during the sweep operation, the beam 115g is closer to the bell of the tube than the beam 1=15b when the deflection is in the direction shown in Figure 15 and is farther away when deflected in the opposite direction, the color purity correction device acts diflterentially on the ray beams and thus permits a substantial degree of selective adjustment or correction of the ray beam travel. 'In this fashion the unit provides color purity even though, as in the case of the unit of Figures 1-9, would seem that color purity would not be improved.

It should be noted that with the coplanar gun arrange.- ment of Figures 1l-l5 the outer ray beams (115g and 1151;) are spaced by a greater distance in the horizontal plane than any of the ray beams with the delta gun arrangement. This accents the selective action of the color purity corrector 121 and is believed to be the reason the unit is more eitective with this type construction than with the delta gun arrangement. Moreover, since the coplanar gun arrangement exhibits less tendency for loss of convergence and color purity under vertical sweep, the adjustment with this type gun arrangement is facilitated.

Figure 10 shows a modified form of the color purity correcting device useful for either the. form of the invention shown in the Figures 1-9 or that shown in Figures 11-15. This form is shown in my co-pending patent application entitled Post Deflection Color Purity Correcting Device for a Color TV Cathode Ray Tube and System Using the Same, Serial No. 648,471, filed March 22, 1957, assigned to the same assignee at the present invention. In this device four magneto straps 201, 202, 203, and 204 are joined together by the nonmagnetic members 205, 206, 207, and 208 to form a ring encircling the bell portion 10b of tube 10 as is shown. The straps have outwardly extending ears 201a, 202a, 203a, and 204a at their ends. The diametrically magnetized magnets 209, 210, 211, and 212 are sandwiched between the ears 201a, 202a, 203a, and 204a, as shown, and are held in position by the L-shaped brackets 213 and the pins 214. Each magnet 209-212 is rotatable about its own axis by reason of the respective pin 214 and is bodily rotatable about an axis radially disposed in relation to the bell 10b by reason of the rivet 213a that carries each of the brackets 213.

With the unit of Figure 10 the influence of each of the magnets 209 to 212, respectively, on the travel of the ray beams is adjustable by rotating the same about its radial axis defined by the pin 213a. The direction of the ray beam deflection is adjusted by rotating each 10 at he .ti ias l sts :20 to 12 sheet t e of it sunk Po t Pil 3- e ppa atus of Figu e l is djusted o p o ide solar Pu y n t same a on as he app ra u of i ur 1-9 and 1l-1 5. However, since the magnetic straps 201 to 20.4 are employed, it is possible with the apparatus of Figure 10, to provide a field component of uniform intensity and orientation extending through the entire bell of the tube. This effect takes place when the orientation of the magnets 209 to 212 is such that the strap 0 for mp spm s a no h Pe e and th strap 194 e mes a sc th Po e Alt tneti ew t e ol ty of straps 2,02 and 204 may be the. opposite, or the straps 2 sa 03 m e ppo n Po The t p 1 202, 203 and 204- may be saturated by the magnets 20 9, 21 211 a 1 o ake Pos ib pposed poles at their po te nds t d fin h u iform fie s m qne t o the tent t m ne adjus ment pr ide uch a ni rm i d r u h. h tube 1 e un f i u e 10 s e t Sh f a h a b ams unif m y a a l P itions of h tt hu N t fi s Qm -wrre t m o de tiqns s e dir eti u tray e n; tr v th t a n form-such as those due to a misalignment of the neck or" the tube in relation to the bell and viewing screen. A 9. uch a fi d te s o rcom a d mpensa for stray magnetic fields within the tube, including the ear ma etic field- -It will, of course, be understood that numerous forms f h color Pur fie m net a m i s 121, and h t of Figure 10 may be used. For example, the magnets may etashablon e d su r which eni les he e Qt h u d simply diu ed y ad ing the same in somewhat the same fashion as wheel weights are used toprovide static and dynamic balance of automobile 'wheels. The significant feature is that the magnets are effective on the respective. ray beams after the same have been deflected, and that the magnets extend generally around the periphery of the tube and be capableof independent adjustment as to orientation and in ns t s h the s c ve re b u and sreeni lq rasters can be made pure in color.

p ar mmut n ac o d nce th e e e in nti n h b n hl uss sst lh re f re; t has been standard practice to attempt to make all ray beams pass through the color centers"? of the tube. These are the P in wh e e ra beama i in per m l ne condition-would intersect the plane; of the field of the deflection yoke (plane 1.375, Figure. 1). In efforts, to secure thisorientation. and, positioning, complicated color pu ty ecto s h e n gt ed a h ne s o the c hode a t e he esu t sb e p u a of d u tme t d n diti it h s ee n ces a term da t s n r a emss st bo h S an's nd d n mi fields (as by the use of windings on the cores 36b, 36g, and 36r, Figure 7) so that the ray beams are, in efiect, recorrected as the sweep progresses. This not only increases the expense of the unit but in addition it entails a great number of adjustments and demands the generation of varying forms of voltages that otherwise would not be necessary. Also, the dynamic convergence coils take power from the ray beam sweep mechanism and thus demand components of increased size.

The advantages of the apparatus of the present invention are particularly marked in the form of the invention shown in Figures 11-15 where the electron guns are in a common plane. For example, in one receiver construction the number of dynamic convergence adjustments was reduced from 12 to 8 with the incident reduction in adjustment time and an improvement in color purity. Moreover, the shadow mask type tube when so constructed can be used with shadow mask openings of greater diameter. In any shadow mask type tube there is a substantial loss of efficiency due to the fact that the shadow mask serves to prevent some electrons from reaching the phosphor screen and creating illumination.

.ingly increased.

. of color purity.

7 11 a The extent of this loss of 'etficiency is determined by the size ofthe openings in'the shadow mask, the larger each opening, the, greater the efficiency. However, one of the limiting factorsin determining the size of these openings is the extent to which convergence error causes the are in the shadow mask the less degradation in color purity results from such error. Conversely, when the degree of convergence is increased-as by the apparatus of the present invention-the size of the openings can be increased without causing electrons from any electron gun to strike the phosphor screen ata point producing the wrong color; The efliciency of the tube is accord- In. addition to the foregoing advantages, the apparatus of the present invention has provided a reduction in the number of rejected tubes, since itmakes possible to shift the raster as much as 1% inch without undue degradation Moreover, the focus of the respective ray beams-is improved and localized deviations from color purity not correctable by the prior apparatus has been found correctable. In addition, the problem of neck shadow is greatly reduced. This is exceedingly important in connection with the formof the invention shown in 'Figures 11 to 15, since one of the problems of having i 12 A television receivers heretoforenot serviceable in the'field canbe serviced. f j a While I have shown and described specific embodiments of the present invention it will, of course, be

respective ray beams to deviate from their intended po- 7 the ray beams at a substantially spaced position is that the greater spread of the beams makes the outside beams strike the bell of the tube at a comparatively small angle of sweep, thus making the neck'shadow problem more acute; It may be added that the apparatus also provides the apparatus of the present invention is that with the delta type gun arrangement of Figures -19, it'usually perts in converging'the receivers to provide optimum,

color purity. The average Serviceman cannot effectively adjust such receivers for convergenceexcept on the basis of an intolerable amount of adjustment, test, readjustment, etc. With the apparatus of the present invention it has been found possible for a reasonably skilled technician to provide adequate color purity in a few minutes, which means not only that the cost of manufacture is greatly reduced buto f equal importance-it has been possible to have a reasonably skilled television repairman make the necessary adjustments so that color a correction for stray magnetic fields such as the earths V magnetic field.

A measure of the practical advantages provided by i understood that various modifications and alternative construction maybe used without departing from the true spirit and scope thereof. Thus the positions of the magnets may be moved towards or away from the shadow mask .to alter the extent the ray beams are deflected sclectively, the phosphor screen may be curved and perhaps coextensive with the face of the tube, the guns in a planar type tube may be aligned vertically, and other variations may be employed. I therefore intend by the appended claims to cover all'such modifications and alternative construction as fall within their true spirit and scope. 7

What I claimias new and desire to secure by Letters Patent of the United States is: a

The process of adjusting a color television receiver for color purity, the receiver having a multi-gun tube in which the color pure operation requires the electron streams to approach the screen as if from predetermined color centers, means to adjust the orientation of the electron streams prior to deflection, and a series of universally rotatable magnets disposed in a ring about the ball of the tube, the process comprising: operating the receiver with deflection and with said magnets parallel tothe direction of ray beam-travel and adjusting the orientations of the electronstreams by said first means to produce light of their respective colors at the center of the viewing "screen; operating the receiver-with sweep and with all but one electron stream suppressed and adjusting said'ma'gnets to' provide a colorpure raster of the color of said one stream; repeating this adjustment for each of the other electron streams to obtain tasters of the respective colors; and repeating the above two adjustments to compensate for interactions between'the successive steps.

References Cited in the file of this patent UNITED STATES PATENTS De Gier et al. -2 Oct. 14, 1941 

